It is known to provide movable and elevatable scaffold assemblies or lifts, for workmen in view of making installations of for example electrical wiring, heating ducts or the like in ceiling structures. Such movable/elevatable scaffold assemblies typically include a wheeled motorized base, a scissor linkage assembly, and a platform supported by the scissor linkage over the base. Hydraulic rams are connected to the scissor linkage in such a way that upon expansion of the hydraulic ram, the scissor linkage extends to elevate the platform. The motorized base usually includes a carriage carried over ground by a front wheel axle and a rear wheel axle, each axle carrying a pair of opposite wheels; and a drive motor driving one of the two front or rear axles.
The problem with such vehicles is to reconcile manoeuvrability with stability. Indeed, on the one hand, as a load is lifted by the platform, the center of gravity of the vehicle progressively moves away spacedly upwardly from the ground. With a higher center of gravity, the vehicle is less stable, particularly if the loading distribution over the platform is unequally provided. Prior art ways of controlling this instability include adding laterally spread apart outrigger wheels, being pivoted to the vehicle ground base and which may also be connected to hydraulic rams for swinging these outrigger wheels from an operative, ground-engaging condition to a raised condition alongside the base. These laterally extended outriggers are destined to prevent the accidental tipping over, swaying and/or tilting of the vehicle when the loaded platform is raised. In addition, to ensure fore and aft stability control of the vehicle, over and above the lateral stability control of the lateral outrigger wheel assembly, the front and rear axles of this vehicle should be as far away as possible from one another.
On the other hand, as the front and rear axles are spread apart for better vehicle stability, the turning radius of the vehicle increases, and thus, the manoeuvrability of the vehicle decreases, particularly in tight spots.